authelia: add the nginx configuration

roles/authelia/templates/authelia.conf.j2

@@ -0,0 +1,15 @@
+server {
+    listen 80;
+    return 301 https://$host$request_uri;
+}
+
+server {
+    server_name auth.{{ base_domain }};
+    listen 443 ssl http2;
+
+    location / {
+        set $upstream_authelia http://authelia:9091; # This example assumes a Docker deployment
+        proxy_pass $upstream_authelia;
+        include /etc/nginx/snippets/proxy.conf;
+    }
+}